1. Field of the Invention
The invention disclosed and claimed herein generally pertains to a method for validating a product or other object, wherein a sensor device such as a vertical array of sensors are used to determine product length. More particularly, the invention pertains to a method of the above type wherein products are successively scanned, and then moved through the sensor array by means of a weighing conveyer. Even more particularly, the invention pertains to a method of the above type that is useful in regulating or controlling transaction speed in a self-checkout conveyer system.
2. Description of the Related Art
There is increasing use of self-checkout systems, by stores and other commercial establishments that seek to handle large volumes of customers with greater efficiency and reduced costs. Such systems can be used with products of many types, provided that bar code labels or the like can be attached thereto, to accurately identify the product types or categories to which respective products belong. In existing self-checkout systems, a scanner is generally available, for use in scanning the bar code labels on each product that a shopper wishes to purchase. After a product is scanned, it is commonly placed on a scale-mounted conveyer, for movement and weighing.
As a product is moved by the weighing conveyer, two sets of sensors may be used to determine one or more product characteristics, and also to detect product motion. In a common arrangement, a front set of sensors comprises a front arch, or vertical array of opposing LEDs and light sensors. The front arch is positioned near the front of the weighing conveyer along the conveyer path of travel. As the conveyer moves the product through the front arch, the light of respective LEDs is blocked or broken, up to a level that indicates the height of the product. A firmware control used with the front arch delivers this height data to a system processor, which also receives product weight information from the weighing conveyer. Software in the processor then compares the height and weight information with reference height and weight information, respectively, for the type or category of product that is identified by the product bar code. The system thus provides two levels of security validation, to confirm that the product is indeed the type of product identified by its bar code. Such validation of a product may be necessary, before the scanner will be enabled to scan further products.
The second set of sensors is generally located toward the rear of the weighing conveyer. This rear set of sensors detects the product transiting off of the weighing conveyer and onto a transport conveyer, or onto some other off-load platform or site. The rear set of sensors frequently comprises a single pair of LEDs and light sensors, or a single flat sensor, and notifies the processor software, via the firmware control, when the product has been transited off of the weighing conveyer. A rear sensor of this type provides only a single break/make indication, that is, only a detection of the beginning and the end of the product as it moves along the conveyer.
In an arrangement using only a single pair of LEDs for the rear sensor, a problem can occur if the product moving along the weighing conveyer is of an irregular or odd shape. In this situation, the rear set of sensors will provide significantly different data than is provided by the front sensor, comprising a vertical LED array as described above. For example, if the product is a bowl, the front LED array will indicate a break sooner than the flat rear sensor will, because of the U-shaped configuration of the bowl. It has been found that software algorithms of the type that are currently used, in order to detect complete transfer of a product from the weighing conveyer to the transport conveyer, tend to be confused by the inconsistent data furnished by the front arch or LED array, and by the flat or single pair rear sensor configuration described above.
One solution to the above problem would be to use a rear arch at the end of the weighing conveyer, rather than a single pair of LEDs, wherein the rear arch was identical to the front arch. In this case, the data sent to the processor software by the firmware control would look the same for both front and rear arches, as a product passed through the respective arches. This configuration has been used in the past. However, it is desirable to avoid use of a second arch if possible, in order to reduce costs.